Conventional fiber optic receivers typically use a transimpedance amplifier to convert the current from the photodetector input device into a voltage. The transimpedance amplifier may include an integrator circuit including a Miller feedback integrator capacitance (C), which is partially or totally comprised of the parasitic capacitance of the integrator circuit itself. The output of the integrator circuit is delivered to a follower circuit which enables the signal to be delivered through a feedback resistor (R) to the input of the integrator circuit. There are two competing goals for such transimpedance amplifiers: one is broad bandwidth, the other is low noise. In order to minimize the noise in such amplifiers the feedback resistance is made as large as possible. Since the noise increases only as the square root of the resistance V.sub.noise =.sqroot.4KTR (where V.sub.noise is the noise voltage density, K is Boltzmann's constant, R is the feedback resistance and T is the temperature), and the gain increases directly with R, the signal to noise ratio is improved by increasing R. However, since the bandwidth ##EQU1## increasing the feedback resistance R decreases BW: doubling R will halve BW. In situations where a compromise value of R cannot be reached to obtain both the desired noise level and bandwidth other approaches must be used. For example, the value of C could be reduced to offset or even exceed the effect of the increase of R so that the desired bandwidth is achieved through reduction of C while the reduced noise level is achieved by the increase of R. This approach may require using a higher speed, lower capacitance silicon process, or a gallium arsenide process which increases dramatically the cost of the components.
Another problem is the difficulty in controlling the bandwidth. Typically, especially in demanding applications, the capacitance C and resistance R are formed within the integrated circuit and are not accessible for external tuning. Further, because of the variation in R and C which occurs as a part of the fabrication process, the actual value of each may vary .+-.20% from the nominal. A variation of 20% for each of R and C results in an overall bandwidth variation of .+-.44% calculated as ##EQU2## While the resistance R could be made physically large enough to trim in order to control bandwidth, this is not a viable option in most cases because the physically larger resistor would introduce more parasitic capacitance and would increase the noise at higher frequencies, the very thing sought to be avoided by including the resistor in the integrated circuit.